A promoter is a specific DNA sequence that is involved in regulating the expression of operably linked downstream coding or other noncoding nucleic acids. In order to efficiently express a foreign gene in genetic modified organism (GMO), promoters exhibiting strong activity under various conditions and in different species have been identified.
Cauliflower mosaic virus (CaMV) 35S promoter is one of the most frequently used constitutive promoters in plant research (Odell et al. Nature 313(6005):810-812 (1985); Benfey, P. N. and N. H. Chua, Science 250(4983):959-966 (1990)). The CaMV 35S promoter, with a length of 343 base pairs, was isolated from a double-stranded cauliflower mosaic virus, in which the TATA box “tatataa” is localized between −32 bp to −26 bp. Another strong constitutive promoter was isolated from the maize Ubi-1 gene. The maize ubiquitin promoter exhibits very strong activity in most monocot tissues and so it is frequently utilized to drive foreign genes and expression cassettes in monocot plants (Cornejo et al. Plant Mol Biol. 23(3):567-81 (1993): Rooke et al. Annals of Applied Biology 136(2): 167-172 (2000): Castillo et al. Bio-Technology 12(13):1366-1371 (1994); Miki et al. Plant Physiology 138(4):1903-13 (2005)). Besides the CaMV 35S and maize ubiquitin promoters, other constitutive promoters used in transgenic plants include NOS and OCS, which were isolated from Ti plasmid of Agrobacterium tumefaciens. Both of these promoters have strong activity in dicots (Ebert et al. Proc Natl Acad Sci USA 84(16):5745-9 (1987); Velten et al. EMBO J. 3(12):2723-30 (1984); De Block et al. The EMBO Journal, 3(8):1681 (1984).). A further monocot promoter is that cloned from the rice actin 1 gene (McElroy et al. The Plant Cell Online 2(2):163-171 (1990)).
However, strong constitutive promoters such as those discussed above can have drawbacks. In some instances, accumulation of heterologous proteins or final metabolites may interrupt the metabolic homeostasis of a transgenic plant, which may result in repressed growth and development, or may even cause death. Furthermore, excess transcripts can result in repression of expression, or ‘transgene silencing’ or ‘co-suppression’ of the transgene (Dietz-Pfeilstetter, A., Plant Science, 179(3): 164-167 (2010); Kooter et al. Trends Plant Sci. 4(9):340-347(1999): Kumpatla et al. Trends Plant Sci. 3(3):97-104 (1998)). To avoid the adverse consequences brought by constitutive promoters in transgenic plants, inducible promoters and tissue specific promoters may be used, such as the light inducible rice original promoter rbcS, which is expressed in leaf and stem, the heat-inducible promoter Gmhsp17 cloned from soybean, the light inducible and green-tissue specific rice promoter Cab1R, the root and seedling specific Pyk10 promoter cloned from Arabidopsis, the fruit specific promoter E-8 cloned from tomato (Lycopersicon esculentum), and the seed specific promoter from the napin gene cloned from Brassica napus (Nomura, M., et al. Plant Mol Biol. 44(1):99-106 (2000); Schoffl, F., et al., Mol Gen Genet. 217(2-3):246-53(1989); Luan, S. and L. Bogorad Plant Cell 4(8): p. 971-81 (1992); Ellerstrom, M., et al. Plant Mol Biol. 32(6): 1019-27 (1996); Krasnyanski, S. F., et al. In Vitro Cellular & Developmental Biology—Plant 37(4):427-433 (2001); Nitz, I., et al. Plant Science, 161(2):337-346 (2001)). However, a disadvantage of most inducible and tissue specific promoters is that their activities are generally weaker than that of constitutive promoters.
The present invention overcomes previous shortcomings in the art by providing tissue specific promoters useful for modulating gene expression in plants.